1. Field of the Invention
This invention relates generally to valves and, more particularly but not by way of limitation, to valves having axially insertable seats and valve closure members.
2. Brief Description of the Prior Art
It is known that sealing surfaces and O-rings disposed on seats and valve closure members of valves are subject to excessive wear when the valve closure member is rotated while engaging the seat. To prevent such wear, various camming mechanisms have been devised for displacing the seat from the valve closure member during the initial rotation of the valve closure member. Examples of such mechanisms are disclosed in U.S. Pat. No. 3,776,505, issued Dec. 4, 1973, to Nakanishi, and in U.S. Pat. No. 3,245,653, issued Apr. 12, 1966, to Laviguer. A problem which has existed with the provision of such cam mechanisms is that such provision can result in an added complexity of the valve and in the assembly thereof.